DE1669713A1 - Process for the production of foam-shaped ethylene copolymers - Google Patents

Description

Our mark O.S. 25 032 vG / Hu Ludwigshafen (Rnein), August 15, 1967

V9rf? .Nren ? Vv Manufacture of shell-shaped / thyleiie (^ polymers

Jirgenstarxü dar invention is a process for the production of Sponge-shaped l-s ^ rleneopolymerisattin with cross-linked parts.

To Hers; hasten ixiij: .i * soriaumförmigen Äthyleneopolymerisaten various Veriaaren known. In one method, which has been introduced, especially in cL · "technique, the copolymers in a koniinuierl be ^ ca _f operating mixing device, for example, in a Krtruier" Sd gf5sc * imclzenen and tying with a flüssigfe ^ oaar gas -'- ve; igen? -: ^ ?. boi'i;' ^.: El, ζ, "-, an aliphatic, EGhlenwaeserstoff f ^ r a F: - norico.ilen8t off compound, and the receive gemiechv ■■ tDfflogei, - ^C:. 3l i ^ iii ^ © rch nozzle aurgipr-Asst * "aob iao Ttrlaassn -. · "Tüse 6 -» -; i; ti.ij * c -i * _T ^ aI uü / cü :? Jsia -D & mpiu ^^ ck des freibaittel ·

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Foams as polyester are often a hindrance ^;

It is also known that the thermal stability of foamed polymers can be achieved by crosslinking the polymers can increase. For example, foam-like polymers can be used with Incorporation and decomposition of peroxides or by treating with * high-energy radiation. The disadvantage here is, however, that the crosslinked products are no longer thermoplastic, so that it is not possible to use such crosslinked products according to continuously working evaporation processes, a.B. to be processed into foams using an extruder. It bestanc hence the problem of producing flexible, elastic foams with a relatively high thermal stability.

It has now been found that foams can be produced by mixing thermoplastic ethylene copolymers in the thermoplastic state with blowing agents at pressures which are above the blowing agent pressure at the mixing temperatures and releasing the homogeneous mixture with particularly advantageous properties, such as copolymers of ethylene x; nd tinyl esters or Esters of unsaturated, copolynerized acids with ethylene, polycyclic acids, and with blowing agent, 2-isoeth, and the mixtures are taut .

for there. · Vtrffehren tignen BiQh CopolymeriiRtii ö # a ethylene vinyl asit FITEM and / OTDR lst # rn roa "ngtsättifltn * it eop ethylene-AXy

Acids "the -" indeeteiis 60 ^ tviotat * p? Osent Ä

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included in polymerized form. Suitable comonomers are, for example, vinyl esters of acids with 2 to 5 carbon atoms or esters of unsaturated acids of alcohols with 1 Ms 20 carbon atoms. Foams made from copolymers of ethylene have advantageous properties
Vinyl acetate or acrylic acid esters ^ Also suitable are ethylene copolymers which, in addition to the esters mentioned, contain, in particular, 10 to 20 percent by weight of the respective unsaturated acid, such as acrylic acid, crotonic acid, fumaric acid and maleic acid, in copolymerized form. For example, copolymers of ethylene containing 5 to 10% acrylic acid and 5 to 10% acrylic acid t-butyl ester in polymerized form are particularly suitable for the production of soft foams with high heat resistance.

Suitable propellants for the Athylencopolymerisate hydrocarbons, halogenated hydrocarbons and chlorofluorocarbon compounds in question, whose boiling points are 25 to 15O ⁰ C below the melting point dee copolymer. The melting point is to be understood here as the crystallite melting point. Suitable
Propellants are, for example, aliphatic or olefinic hydrocarbons with 3 to 5 carbon atoms, such as propane, butane, pentane or propene, butene or pentene. Of particular importance as a blowing agent have isobutane or hydrocarbons having 5 to 7 carbon atoms and at least two pendant methyl groups, whose boiling points are between -10 and +60 ⁰ C. Neopentane and 2,2-dimethylbutane, for example, are suitable. Of the halogenated hydrocarbons, especially those with 1 or 2 carbon atoms, such as methyl chloride, ethyl chloride, dichloromethane, are suitable.

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Suitable chlorofluorocarbon compounds are dichlorodifluoromethane, Fluorotrichloromethane, monofluorochloromethane, 1,2,2-trifluorotrichloroethane and 1,1,2,2-tetrafluorodichloroethane.

The amounts of blowing agent used are such that the mixtures of thermoplastic ethylene copolymers and blowing agent 15 up to 35 percent by weight of the blowing agent, based on 100 parts of copolymerizate. The amount of propellant is directed according to the desired density of the foamed ethylene copolymer and the pressure and temperature conditions: rend processing. In addition to the propellants mentioned, gas-releasing solid propellants can also be used by themselves alone or in combination with the liquid propellants mentioned above be used.

Solid propellants which are formed at foaming temperatures of gaseous products are e.g. substances that split off nitrogen, such as azo compounds, e.g. azodicarbonamide or azoisobutyric acid dinitrile or aromatic sulfohydrazides.

The ethylene copolymers are expediently 0.5 to 5, preferably 1 to 2 percent by weight of polyisocyanates, based on the weight of the copolymer, mixed.

Aliphatic and aromatic diisocyanates, such as hexamethylene-1,6-diisocyanate, are particularly suitable for the polyisocyanates. Diphenylmethane-4,4'-diisocyanate, naphthylene-1,5-diisocyanate and

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Toluylene-2,4-diisocyanate.

4,4'-dicyclohexylmethane diisocyanate and 3,3'-dimethyl-4,4'-dicyelohexylmethane diisocyanate are particularly suitable.

The residence time of the mixtures of copolymer and polyisocyanate in the mixing zone should advantageously be 2 to 30 minutes.

For the production of foams with a particularly fine cell structure So-called nucleating agents can be added to the mixtures. For example, finely powdered silicates such as talc, which is most expediently used in amounts of 1 to 3 percent by weight, based on the copolymer.

In addition to the copolymer, polyisocyanate and the blowing agent, the mixtures can contain other components, such as fillers, dyes, Contain flame retardants, antistatic agents, stabilizers, lubricants or other polymers. Other polymers For example, polyethylene, polypropylene, polybutene and polyisobutene can be used in amounts up to 40 percent by weight on the copolymer, the mixtures can be added.

The thermoplastic ethylene copolymers are mixed in the thermoplastic state with polyisocyanates and the blowing agents. Suitably the reaction is carried out at temperatures which 10 to 100 ⁰ C, in particular 30 to 90 ⁰ C above the Krietallit-Bchmelzpunktee of the polymers are. The mixes will

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kept under pressures that are above the propellant pressure of the propellant lie at the mixing temperature, so that the propellants are constantly in the liquid state under the mixing conditions are present. Propellant pressure is to be understood as meaning the vapor pressure of the propellant above the molten copolymer. the After the end of the mixing process, mixtures are made homogeneously Relaxed state. This is to be understood as meaning that the mixtures are brought into a zone in which the pressure is below the propellant pressure is at the mixing temperature. Most expediently, the mixture is relaxed under normal conditions standing zone. To produce the mixture, it is advantageous to use continuously operating mixing devices. Of these, extruders (screw presses) have proven particularly useful. The dimensions of the mixer are like this to choose that when leaving the mixing space and entering the relaxation zone, a homogeneous mixture of ethylene copolymer, formed the additives and propellants. The mixtures can also be used in discontinuously operating devices, e.g. in pressure vessels with a stirrer. According to the method of the invention, foams different shape can be obtained. For example, endless foam profiles such as sheets, blown films or Get pipes. The process is also suitable for sheathing Objects with foam-shaped plastic.

Depending on the degree of crosslinking and temperature, the homogeneous mass of copolymer, polyisocyanate and blowing agent is immediately in front

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Open-cell, closed-cell or partially open-cell foams can be obtained by pressing. To produce open-cell foams, the homogeneous mass is brought to a temperature between the crystallite melting point and 20 ° C. immediately before being pressed out. Holding the mass at temperatures τοη at least 30 ⁰ C below the crystallite melting point, closed-cell foams can be obtained. High degrees of crosslinking, about over 30 #, promote the production of open-cell, low degrees of crosslinking, about between $ 10 and $ 30, the production of closed-cell foams.

The process for the production of finely divided ones is of particular importance Foams too. This can be done, for example, by continuously pressing out the mixtures to be foamed and dividing them the mixture before foaming. Foam particles are obtained by the liquid propellant process with diameters between 3 and 20 mm, the tree weight of which can be over 8 g / l, preferably between 10 and 40 g / l. With solid propellants, foams with a density of 100 to 600 g / l are obtained. Such foam particles can be used, for example, as Fillers can be used for upholstery, insulation or as soil loosening agents. Manufactured by welding the particles Sheets or foils are used for heat and sound insulation.

The foams obtained by the process have a gel content which can be between 10 and 70 #. Below gel content the insoluble fractions are to be understood, which are

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be determined, by dissolving the polymer in decalin at temperatures of 14O ⁰ C. The foams obtained have a thermal stability which is 20 to 30 ^° C. higher than the thermal stability of foams which have only been produced using the copolymers. It was surprising that the mixtures to be foamed according to the invention can be pressed out through nozzles and foamed despite the high gel content. In comparable foaming processes in which, for example, ethylene polymers are crosslinked with peroxides, it is only possible to squeeze out mixtures to be foamed with a gel content of 5 to 7 $ through a nozzle and foam them. Such processing is no longer possible if the gel content is higher.

The parts mentioned in the examples are parts by weight.

example 1

100 parts of a copolymer of 85 parts of ethylene and 15 parts of tert-butyl acrylic acid are mixed with 3 parts of talc and 2 parts of diphenylmethane-4,4'-diisocyanate. 12 parts of this mixture are plasticized in a twin-screw extruder with the addition of 2.5 parts of an i-butane / n-butane mixture (50:50). The residence time in the extruder is 2 1/2 min., The maximum temperature of 160 to 17O ⁰ C. The homogeneous polymer blowing agent mixture is extruded through a round die of 3 diameter. The intumescent, closed-cell strand turns into particles through a hot die

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crushed.

The foam particles have a diameter of 15 to 20 mm and a gel content of 15 ^. They have a thermal stability of up to 125 ^° C

A foam prepared without diisocyanate is only to 9O ⁰ C heat stable.

After superficial heating with hot air to 108 ^° C., the crosslinked particles can then be welded in a press to form a foam block with a density of 33 g / l. In the case of non-crosslinked foam particles, due to the lack of heat resistance during hot-air treatment, the particles already shrink considerably; a foam block produced therefore has a significantly higher density of 100 g / l.

Example 2

100 parts of a copolymer of 85 parts of ethylene, 6.5 parts Tert-butyl acrylate and 8.5 parts of acrylic acid are mixed with 3 parts of talc and 2 parts of naphthylene-1,5-diisocyanate. 60 parts of this mixture are plasticized per hour in an extruder and 12 parts of a blowing agent mixture a, consisting of 90 parts of i-butane and 10 parts of dichlorodifluoromethane mixed in. The one by a dog nozzle with a large number open-cell foam strands extruded from 3 mm holes, whose Temperature shortly before foaming about the crystalline element

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temperature, are crushed after cooling by a chopping device to a flaky, open-cell material, which is suitable as a soil loosening agent, for example because of its high water absorption capacity of 500 io of its own weight. The gel content, measured on the finished foam material, is $ 66.

Example 3

100 parts of a mixture of 80 parts of an ethylene vinyl acetate copolymer containing 8 parts of vinyl acetate in polymerized form and 20 parts of polyisobutene are mixed with 0.5 ° azodicarbonamide as the nucleating agent and 1 part of triphenylmethane-4,4 ', 4 "-triisocyanate From 20 parts of a propellant mixture of 70 parts of i-butane and 30 parts of neopentane, the mixture is plasticized and homogenized in a single-screw extruder with a homogenizer and extruded through a multi-hole nozzle,

The exiting foam strands are cut through a hot die, which is attached directly to the nozzle, shredded.

At an extrusion temperature of 170 ⁰ G in the homogenizing and a residence time of 20 minutes, the foam particles have a gel content of 20 $>. The heat resistance is 25 ⁰ O above the value determined on foams obtained without diocyanate.

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Example 4

100 parts of a terpolymer, consisting of 85 parts of ethylene, 10 parts of ethyl acrylate and 5 parts of acrylic acid are mixed with 2 percent by weight of talc and 0.2 percent by weight of azodicarbonamide.

100 kg of this mixture are added hourly in a single-screw extruder with an upstream residence time extruder with the addition of 2,4-toluene diisocyanate plasticized, the isocyanate being im Liquid propellant i-butane is dissolved in such a concentration that with the hourly added propellant amount of 20 kg 1.5 percent by weight of diisocyanate, based on the starting product, can be incorporated.

With a dwell time of 20 minutes and a peak temperature of 165 ° C, a violin holding of $ 30 is achieved. The ones under pressure Standing, crosslinked melt containing blowing agent is released before relaxation brought out of the nozzle to a temperature which is about 30 C below the crystallite melting point of the polymer. At the Ent- ^ j clamp from a slot nozzle with the dimensions 3 mm χ 200 mm, a closed-cell foam tape measuring 1.5 cm × 80 cm and having a density of 25 g / l is obtained.

The heat resistance is about 20 to 25 ° C above that without the addition of diisocyanate produced foam.

Example 5

100 parts of a terpolymer consisting of 80 parts of ethylene ^

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10 parts of n-butyl acrylate and 10 parts of free acrylic acid are introduced in the molten state into a pressure stirring vessel via a gear pump and from there with 3 parts of talc, 2.5 parts of diphenylmethane-4,4 ^f -diisocyanate and 15 parts of a propellant mixture 50 parts of i-butane, 40 parts of propane and 10 parts of neopentane were homogenized. The residence time in the boiler is 25 min., The temperature of 17O ⁰ C.

The homogeneous mixture containing gel fractions is then conveyed via a cooled line by means of another gear pump with an output of 60 l / hour to a round nozzle with a diameter of 10 mm, where it is relaxed at a temperature of 12 ° C. below the melting point of the starting polymer. Here, an endless, closed to 60 i »foam strand diameter of 80 mm is formed.

The density is 25 g / l, the gel content 25 to 30 #.

The heat resistance is 30 ⁰ C above the made of the non-network-th starting polymer foam.

Example 6

100 parts of a mixture consisting of 90 parts of a copolymer of 85 percent by weight of ethylene and 15 percent by weight of n-hexyl acrylate, and 10 parts of polypropylene, are mixed with 3 i ° talc as a nucleating agent and 4 percent by weight of naphthylene diisocyanate and 60 kg of this per hour in a double

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screw extruder with metered addition of 12 kg of methyl chloride with a residence time of 5 minutes and an extruder temperature of 170 C plasticized and homogenized.

The pressurized melt containing blowing agent has a gel content of $ 40>. It is depressurized to normal pressure at a temperature which is 25 ° C. below the crystallite melting point of the ethylene copolymer via a slot nozzle measuring 0.3 mm 200 mm. A closed-cell flat foam tape with a cross section of 1 mm × 700 mm is obtained.

The tensile strength of this flat belt in the longitudinal direction is about 10 kg / cm and in the transverse direction is 4 kg / cm.

The heat resistance of 120 ⁰ C. The foam sheet is suitable as a replacement for Verpackung3decken in the removals.

Example 7

100 parts of a copolymer of 90 parts of ethylene and 10 parts of t-butyl acrylate are mixed with 2 parts of azodicarbonamide, 5 Parts of zinc oxide and 3 parts of talc and 2 parts of diphenylmethane-4,4'-diocyanate mixed. 20 parts of the mixture are plasticized per hour in a single-screw extruder, the one has a suitable device for cable sheathing. The temperature is adjusted so that the decomposition of the solid propellant B. takes place near the nozzle. The gas dissolved in the pressurized melt escapes when the pressure is released into a zone of low pressure and forms one around the neutral metal cable

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1.5 mm thick foam jacket with a density of 100 g / l. The gel content of the foam is 30 56.

Example 8

100 parts of a mixture of 90 parts of a vinyl acetate-ethylene copolymer with 15 percent by weight of vinyl acetate and 10 parts of polybutene, together with 2 parts of ρ, ρ'-oxy-bi - benzenesulfohydrazide and 1.5 parts of naphthylene-1,5-diisocyanate Plasticized in an extruder and through a film blowing nozzle relaxed. The resulting foam crosslinked to 20 56 becomes a foamed very soft film of 500 / u strength and one Blow up density of 80 g / l.

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Claims (2)

- 15 - O.Z. 25 032 claims 1669713 1. A process for producing heat-resistant foams by mixing thermoplastic ethylene copolymers in the thermoplastic state with blowing agents at pressures which are above the blowing agent pressures at the mixing temperatures and releasing the homogeneous mixtures, characterized in that copolymers of ethylene and vinyl esters or esters of unsaturated acids with Polyisocyanates and mixed with blowing agent and the mixtures relaxed. 2. The method according to claim 1, characterized in that one works at mixing temperatures ^{of over 150 0 C.} Badische Anilin- & Soda-Fabrik AG 109813/1716